Apple iMovie 8.0.5 update debuts new iFrame video format

Apple has created a new video format called iFrame for use by camcorders, allowing optimized import into iMovie for editing.

A support article describing the new format, which was just added to iMovie 09 in the 8.0.5 update, says the new iFrame Video format "is designed by Apple to speed up importing and editing by keeping the content in its native recorded format while editing. Based on industry standard technologies such as H.264 and AAC audio, iFrame produces small file sizes and simplifies the process of working with Video recorded with your camera."

Support for the new format was announced by Sanyo, which has added iFrame recording to two of its new camcorders introduced today, the HD2000A and FH1A.

The new iFrame format captures standard H.264 video at 960x540, a quarter the resolution of full 1080 HD. The new cameras from Sanyo default to record in the iFrame format, but can also be set to record in full 1080 HD.

Finding a format

Digital camcorders began recording in MJPEG (Motion JPEG, a series of still photo captures) before moving to the better compression of the popular DV format. While DV recording allowed for high quality capture, it wasn't optimally designed for direct editing in QuickTime; it uses non-square pixels and is oriented toward TV resolutions and aspect ratios.

JVC improved upon the consumer DV format with its HDV format (also supported by Canon Sony and Sharp) using MPEG-2 video similar to a DVD, although HDV uses a transport stream rather than a program stream (like DVD), as it is optimized for delivery rather than storage. The recording format is also optimized for playback rather than editing. Importing HDV into iMovie using an intermediate codec makes editing more efficient, but also requires more disk space.

A variety of other competing digital formats have appeared on the high end, including Panasonic's DVCPRO HD (based on DV encoding) to Sony's DVCAM (also based on DV) and XDCAM EX (using MPEG-2).

Panasonic and Sony paired up to create the AVCHD format, which is based on modern MPEG-4 H.264 video. However, AVCHD still multiplexes its audio and video into an MPEG transport stream rather than recording it as a standard MPEG-4 file. In order to edit the AVCHD video captured by camcorders, iMovie still has to import and transcode it into the Apple Intermediate Codec, which requires time and consumes lots of disk space. Final Cut Pro similarly imports AVCHD video into AppleProRes.

By floating the new iFrame format using the same standard MPEG-4 H.264 video, Apple hopes to simplify the import process for consumers, making it easier and faster to ingest camcorder video for editing.

The name of the new format appears to reference both Apple's consumer product line and MPEG's I-frames, or intraframes, which act as keyframes in the video recording. Between full I-frames, MPEG compression uses P-Frames or predictive frames, which only present what has changed since the last I-frame, as well as B-frames, or bidirectional predictive frames. These present part of a picture like a P-frame, but reference changes relative to a future frame. In other words, B-frames come in advance of an I or P-frame that fills in the missing details.

The difference between MPEG4/QuickTime and AVCHD isn't in media multiplexing. It's how the table of contents is stored.

AVCHD is in an MPEG2 streaming format comprised of blocks of media, with each block having its own short description. Cameras can record this format without needing to buffer anything more than the current block of media. Random-access playback requires a scan through the file to build a table of contents. It does not need to be imported before editing as Apple would like you to think. Importing is performed because QuickTime does not support certain H.264 extensions in AVCHD.

The MPEG4/QuickTime file format has one contiguous table of contents. That's great for random access playback but awful for everything else. To produce an MPEG4, a camera would have to write raw data and metadata to two files during recording. When the stop button is pushed, the camera would have to copy the two components to a single file, re-index the metadata into table of contents, then delete the two component files. It's a long process that would make the camera unresponsive and prone to data loss.

I welcome faster imports and to be honest, I think that will satisfy most families recording family memories. I don't have ulimited HDD space and more importantly, backing up video projects to multiple drives isn't quick either.

We need faster cabling, quicker hdd access, and larger hdd's if I am going to waste my time recording a new tooth from my kiddy in 1080p and then doing everything that goes along with it (importing to backing up) in a timely fashion.

AVCHD is in an MPEG2 streaming format comprised of blocks of media, with each block having its own short description. Cameras can record this format without needing to buffer anything more than the current block of media. Random-access playback requires a scan through the file to build a table of contents. It does not need to be imported before editing as Apple would like you to think. Importing is performed because QuickTime does not support certain H.264 extensions in AVCHD.

Huh? AVCHD is NOT MPEG-2, it is MPEG-4 PART 10 (that is: it uses H.264/AVC compression) and practically everything you wrote is wrong. AVCHD uses interframe and intraframe compression and therefore it must be decoded for editing, as most frames do not include all picture data. Even the Sony Vegas software that pretends to edit AVCHD "natively" does internally read in entire GOPs, calculates each single frame and then edits. It just does it "on-the-fly", while Apple does it on import. AVCHD is not an editing format, it is a distribution format and editing will always require the software to fill up the partial frames first.

I'd be curious to hear about whether/how iFrame lives up to its promise, from movie pros.

Well, it is not intended for "movie pros" - it is designed for consumers who want to skip any import/conversion steps before editing and be able to post footage to YouTube, etc. in no time. If it works as advertised, it should fit that bill just fine.

I welcome faster imports and to be honest, I think that will satisfy most families recording family memories. I don't have ulimited HDD space and more importantly, backing up video projects to multiple drives isn't quick either.

We need faster cabling, quicker hdd access, and larger hdd's if I am going to waste my time recording a new tooth from my kiddy in 1080p and then doing everything that goes along with it (importing to backing up) in a timely fashion.

Can't disagree with you on file size. AVCHD converted to ProRes grows dramatically in size.

As for imports, the ingestion process that FC7 employs pretty much happens in real time or so on my 2.4Ghz iMac (saving up for a MacPro). My solution for backups is that I shoot on 8GB SD cards pretty much all the time and burn the raw footage to a DVD-9 (until I get a Blu-ray drive).

Editing HD does tax my iMac but I can usually crank out quick little 15-minute videos on Blu-ray formatted DVD's without expending too much time or effort.

With that said, I can certainly see why Apple would introduce their own format for the masses. Something that can be edited quickly, is relatively small in size and has better-than-DVD quality (if only slightly) will most likely be good enough for most iMovie users out there.